Chemistry ⚗️

• The pH scale is logarithmic, meaning that each whole number change represents a tenfold increase or decrease in acidity/alkalinity.
• A solution with a pH of 7 is neutral (neither acidic nor alkaline).
• Acids have a pH less than 7, while bases have a pH greater than 7.
• Strong acids completely dissociate into hydrogen ions (H+) and anions when they are dissolved in water.
• Reduction in use, reuse and recycling of materials by end users


  Reduces the use of limited resources, use of energy sources, waste and environmental impacts
• Metals, glass, building materials, clay ceramics and most plastics are produced from limited raw materials
• Much of the energy for the processes comes from limited resources
• Obtaining raw materials from the Earth by quarrying and mining causes environmental impacts
• Some products

  • Can be reused, e.g. glass bottles can be crushed and melted to make different glass products
• Other products


  • Cannot be reused and so are recycled for a different use
• Metals


  • Can be recycled by melting and recasting or reforming into different products
• The amount of separation required for recycling depends on the material and the properties required of the final product
• Some scrap steel can be added to iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore
• Life cycle assessment (LCA)


  Carried out to assess the environmental impact of products in each stage: extracting and processing raw materials, manufacturing and packaging, use and operation during its lifetime, disposal at the end of its useful life, including transport and distribution at each stage
• Use of water, resources, energy sources and production of some wastes can be fairly easily quantified
• Allocating numerical values to pollutant effects is less straightforward and requires value judgements, so LCA is not a purely objective process
• Selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, e.g. in support of claims for advertising purposes
• Sewage treatment


  1. Screening and grit removal

  2. Sedimentation to produce sewage sludge and effluent

  3. Anaerobic digestion of sewage sludge

  4. Aerobic biological treatment of effluent
• The Earth's resources of metal ores are limited
• Phytomining


  Uses plants to absorb metal compounds, then the plants are harvested and burned to produce ash that contains metal compounds
• Bioleaching


  Uses bacteria to produce leachate solutions that contain metal compounds
• The metal compounds can be processed to obtain the metal, e.g. copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis
• Potable water


  Water that is safe to drink, with sufficiently low levels of dissolved salts and microbes
• Producing potable water in the UK

  1. Choosing an appropriate source of fresh water

  2. Passing the water through filter beds

  3. Sterilising
• Sterilising agents for potable water

  Chlorine, ozone or ultraviolet light
• Desalination


  Producing potable water from salty water or sea water, by distillation or processes that use membranes such as reverse osmosis
• Desalination processes require large amounts of energy
• Humans use the Earth's resources to provide warmth, shelter, food and transport
• Natural resources, supplemented by agriculture, provide food, timber, clothing and fuels
• Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials
• Chemistry plays an important role in improving agricultural and industrial processes to provide new products and in sustainable development, which is development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
• Examples of natural products that are supplemented or replaced by agricultural and synthetic products

  • Not provided
• Finite and renewable resources

  • Not provided
• Carbon monoxide


  A toxic gas, colourless and odourless
• Sulfur dioxide and oxides of nitrogen

  Cause respiratory problems in humans and cause acid rain
• Particulates


  Cause global dimming and health problems for humans
• Combustion of fuels


  Produces carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen, as well as solid particles and unburned hydrocarbons
• Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur
• Human activities that increase the amounts of greenhouse gases carbon dioxide and methane in the atmosphere

  • Not provided
• Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth's atmosphere to increase at the surface and that this will result in global climate change